How do I deal with technical difficulties and how do I know I have practice the right way?

I am a relatively late starter on the piano and often have to deal with difficult passages such as playing both melody and accompaniment with only one hand. I'm learning Beethoven Sonata Op 27 no.1, first movement. I have some problems with phrasing the top line melody especially the part where the cadences are.

My teacher taught me to use my whole arm to play and rotate my elbow a little to bring out the top line melody. It did work but the inner 'block chords' can't be heard clearly or sometime the tones are uneven. There are also times where I have clumsy fingers playing fast passages and huge octave leaps. I did practice slowly with metronome. Despite the fact that my teacher encourage me all the time, my playing is still very much inconsistent each time I play for him.

Any suggestions that will help me practice more effectively? Eventually I will have to perform for a student concert and I do not want any slips and missing details in my playing that I have previously. Thanks!!

You have Grade VII. You are already a good pianist!!

To get better:

Read all the good books you can find on piano technique and practice, but make up your own mind about who has got it right (because opinions often conflict). Listen to as many fine performances as you can. Better still watch videos and live performances (but avoid too much exposure to much of the junk and really bad stuff on YouTube). Study the works you want to play in detail and annotate the scores, not only with fingerings but with notes about how you can achieve the sound you want. Use the metronome sparingly. Practice as much as possible - but not when you are too tired to concentrate. Vary your tempo. Vary your surroundings. Eliminate bad habits by practicing the correct movements over and over until they are more strongly ingrained than the old ones. If you neeed to go back to basics to learn control, relaxation, and poise then do it! (Feuchtwanger's exercises are good). Find technical exercises and studies for any specific dificulties you have in your repertoire. Take frequent short breaks when practicing to keep up concentration. Get enough sleep for the unconscious mind to sort out what you have learned during the day. Practice on the finest instrument you can find or afford (but don't depise an inferior instrument or digital keyboard if that is what you have to use for whatever reason). Immerse yourself in the piano and its culture. But don't negelect to continue to study music alongside the physical skill of making sounds on the piano. Don't, drink, don't smoke. Get some aerobic exercise to keep fit (but don't overdo it - you are a pianist - not an athlete). Then be patient. It still takes years.

** Tries to hide ashtray down back of piano **

One thing I've learnt by restarting piano lessons in adulthood is to be very focused on my practice. For example at the moment I'm concentrating on a few awkward chord passages in a piece I'm studying to ensure I get them 100% accurate which means going over & over these passages until it is second nature. As a child I used to just keep playing my pieces through thinking I was practising, but I wasn't. I was just repeating all my mistakes over & over again without concentrating on the parts I was getting wrong eg pedalling, fingering, notes,tone etc etc. I work out what I want to achieve from my practice and then decide my course of action to hopefully reach my goal.